== The BZ angle in e+ e-  -> 4jets: abelian vs non-abelian ==

Use MadGraph/MadEvent to produce two event samples,
one for standard QCD and one with an abelian QCD model for



Run the collision on the peak of the Z boson and set a minimum invariant mass
for the jets of $m_{jj}>10$ GeV. Plot the
Bengtsson-Zerwas angle between the planes identified by the two lowest and to highest 
energy jets:

%$
\cos \chi_{BZ} = 
\frac{( {\bf p}''1\times {\bf p}''2) \cdot  ({\bf p}''3\times {\bf p}''4)}
{||{\bf p}''1 \times {\bf p}''2 || ||{\bf p}''3\times {\bf p}''4||}\,.
$%

Comparison should be made with the plots of Ref. [http://arxiv.org/abs/hep-ph/9503354 hep-ph/9503354], 
where various implementation of the abelian models are discussed. Our web implementation include the emission of abelian gluons as possible partons leading to jets. 


-- Main.FabioMaltoni - 29 Aug 2007